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authorGustavo A. R. Silva <gustavoars@kernel.org>2021-08-04 22:45:36 +0200
committerDavid S. Miller <davem@davemloft.net>2021-08-05 12:46:42 +0200
commitdb243b796439c0caba47865564d8acd18a301d18 (patch)
tree4d9286e7e1146337ff111a5cf0b2552dc9cc5195 /net/ipv4/ip_sockglue.c
parentMerge branch 'bridge-ioctl-fixes' (diff)
downloadlinux-db243b796439c0caba47865564d8acd18a301d18.tar.xz
linux-db243b796439c0caba47865564d8acd18a301d18.zip
net/ipv4/ipv6: Replace one-element arraya with flexible-array members
There is a regular need in the kernel to provide a way to declare having a dynamically sized set of trailing elements in a structure. Kernel code should always use “flexible array members”[1] for these cases. The older style of one-element or zero-length arrays should no longer be used[2]. Use an anonymous union with a couple of anonymous structs in order to keep userspace unchanged and refactor the related code accordingly: $ pahole -C group_filter net/ipv4/ip_sockglue.o struct group_filter { union { struct { __u32 gf_interface_aux; /* 0 4 */ /* XXX 4 bytes hole, try to pack */ struct __kernel_sockaddr_storage gf_group_aux; /* 8 128 */ /* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */ __u32 gf_fmode_aux; /* 136 4 */ __u32 gf_numsrc_aux; /* 140 4 */ struct __kernel_sockaddr_storage gf_slist[1]; /* 144 128 */ }; /* 0 272 */ struct { __u32 gf_interface; /* 0 4 */ /* XXX 4 bytes hole, try to pack */ struct __kernel_sockaddr_storage gf_group; /* 8 128 */ /* --- cacheline 2 boundary (128 bytes) was 8 bytes ago --- */ __u32 gf_fmode; /* 136 4 */ __u32 gf_numsrc; /* 140 4 */ struct __kernel_sockaddr_storage gf_slist_flex[0]; /* 144 0 */ }; /* 0 144 */ }; /* 0 272 */ /* size: 272, cachelines: 5, members: 1 */ /* last cacheline: 16 bytes */ }; $ pahole -C compat_group_filter net/ipv4/ip_sockglue.o struct compat_group_filter { union { struct { __u32 gf_interface_aux; /* 0 4 */ struct __kernel_sockaddr_storage gf_group_aux __attribute__((__aligned__(4))); /* 4 128 */ /* --- cacheline 2 boundary (128 bytes) was 4 bytes ago --- */ __u32 gf_fmode_aux; /* 132 4 */ __u32 gf_numsrc_aux; /* 136 4 */ struct __kernel_sockaddr_storage gf_slist[1] __attribute__((__aligned__(4))); /* 140 128 */ } __attribute__((__packed__)) __attribute__((__aligned__(4))); /* 0 268 */ struct { __u32 gf_interface; /* 0 4 */ struct __kernel_sockaddr_storage gf_group __attribute__((__aligned__(4))); /* 4 128 */ /* --- cacheline 2 boundary (128 bytes) was 4 bytes ago --- */ __u32 gf_fmode; /* 132 4 */ __u32 gf_numsrc; /* 136 4 */ struct __kernel_sockaddr_storage gf_slist_flex[0] __attribute__((__aligned__(4))); /* 140 0 */ } __attribute__((__packed__)) __attribute__((__aligned__(4))); /* 0 140 */ } __attribute__((__aligned__(1))); /* 0 268 */ /* size: 268, cachelines: 5, members: 1 */ /* forced alignments: 1 */ /* last cacheline: 12 bytes */ } __attribute__((__packed__)); This helps with the ongoing efforts to globally enable -Warray-bounds and get us closer to being able to tighten the FORTIFY_SOURCE routines on memcpy(). [1] https://en.wikipedia.org/wiki/Flexible_array_member [2] https://www.kernel.org/doc/html/v5.10/process/deprecated.html#zero-length-and-one-element-arrays Link: https://github.com/KSPP/linux/issues/79 Link: https://github.com/KSPP/linux/issues/109 Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4/ip_sockglue.c')
-rw-r--r--net/ipv4/ip_sockglue.c19
1 files changed, 10 insertions, 9 deletions
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index 468969c75708..b297bb28556e 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -790,7 +790,8 @@ static int ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval, int optlen)
goto out_free_gsf;
err = set_mcast_msfilter(sk, gsf->gf_interface, gsf->gf_numsrc,
- gsf->gf_fmode, &gsf->gf_group, gsf->gf_slist);
+ gsf->gf_fmode, &gsf->gf_group,
+ gsf->gf_slist_flex);
out_free_gsf:
kfree(gsf);
return err;
@@ -799,7 +800,7 @@ out_free_gsf:
static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
int optlen)
{
- const int size0 = offsetof(struct compat_group_filter, gf_slist);
+ const int size0 = offsetof(struct compat_group_filter, gf_slist_flex);
struct compat_group_filter *gf32;
unsigned int n;
void *p;
@@ -813,7 +814,7 @@ static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
p = kmalloc(optlen + 4, GFP_KERNEL);
if (!p)
return -ENOMEM;
- gf32 = p + 4; /* we want ->gf_group and ->gf_slist aligned */
+ gf32 = p + 4; /* we want ->gf_group and ->gf_slist_flex aligned */
err = -EFAULT;
if (copy_from_sockptr(gf32, optval, optlen))
@@ -826,7 +827,7 @@ static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
goto out_free_gsf;
err = -EINVAL;
- if (offsetof(struct compat_group_filter, gf_slist[n]) > optlen)
+ if (offsetof(struct compat_group_filter, gf_slist_flex[n]) > optlen)
goto out_free_gsf;
/* numsrc >= (4G-140)/128 overflow in 32 bits */
@@ -834,7 +835,7 @@ static int compat_ip_set_mcast_msfilter(struct sock *sk, sockptr_t optval,
if (n > sock_net(sk)->ipv4.sysctl_igmp_max_msf)
goto out_free_gsf;
err = set_mcast_msfilter(sk, gf32->gf_interface, n, gf32->gf_fmode,
- &gf32->gf_group, gf32->gf_slist);
+ &gf32->gf_group, gf32->gf_slist_flex);
out_free_gsf:
kfree(p);
return err;
@@ -1455,7 +1456,7 @@ static bool getsockopt_needs_rtnl(int optname)
static int ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
int __user *optlen, int len)
{
- const int size0 = offsetof(struct group_filter, gf_slist);
+ const int size0 = offsetof(struct group_filter, gf_slist_flex);
struct group_filter __user *p = optval;
struct group_filter gsf;
int num;
@@ -1467,7 +1468,7 @@ static int ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
return -EFAULT;
num = gsf.gf_numsrc;
- err = ip_mc_gsfget(sk, &gsf, p->gf_slist);
+ err = ip_mc_gsfget(sk, &gsf, p->gf_slist_flex);
if (err)
return err;
if (gsf.gf_numsrc < num)
@@ -1481,7 +1482,7 @@ static int ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
static int compat_ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
int __user *optlen, int len)
{
- const int size0 = offsetof(struct compat_group_filter, gf_slist);
+ const int size0 = offsetof(struct compat_group_filter, gf_slist_flex);
struct compat_group_filter __user *p = optval;
struct compat_group_filter gf32;
struct group_filter gf;
@@ -1498,7 +1499,7 @@ static int compat_ip_get_mcast_msfilter(struct sock *sk, void __user *optval,
num = gf.gf_numsrc = gf32.gf_numsrc;
gf.gf_group = gf32.gf_group;
- err = ip_mc_gsfget(sk, &gf, p->gf_slist);
+ err = ip_mc_gsfget(sk, &gf, p->gf_slist_flex);
if (err)
return err;
if (gf.gf_numsrc < num)